An air conditioner having a light wave unit for auxiliary heating and sterilizing is provided, which comprises a conventional air conditioner including a filter (8), an evaporator (5), a cross-flow fan (6) and a motor (9). The light wave unit includes a light wave tube (2), a temperature sensor (4) and a controller (7). The light wave tube is provided between the evaporator (5) and the cross-flow fan (6), the temperature sensor (4) is mounted on the evaporator (5), and an input port of the controller (7) is coupled to a signal output port of the temperature sensor (4) while an output port of the controller (7) is coupled to a power input port of the light wave tube (2). The advantage of the air conditioner is that the light wave tube is provided to fulfill an auxiliary heating and sterilizing operation. The air conditioner can overcome not only the defects with an ultraviolet unit in the art that are harmful to a human body and causes materials to be aged, but also the defects with an ozone unit in the art that will generate ozone pollution and a high-voltage. The air conditioner is friendly to the environment and convenient for users.